Epidemiologic studies have demonstrated a greater prevalence of essential hypertension (EH) in blacks and a disproportionately far greater mortality related to EH in blacks. The identification and delineation of participating mechanisms governing the evolving pathogenesis of EH in blacks would open avenues for application of non-pharmacologic prophylactic and preventive measures. The objectives of this proposed 3 year program are 1) to investigate the interaction of biobehavioral factors in relation to blood pressure control in a representative young black population and representative white population, 2) to study the interactive biobehavioral factors in blacks at high risk for EH (borderline EH) and 3) to evaluate the association between biobehavioral factors and prospective correlates of EH in these groups. The population will consist of blacks and whites who were originally enrolled in the Collaborative Perinatal Project (CPP), were then followed longitudinally in adolescence and are now in a continued longitudinal study at age 17-21 years. In our study groups we will study the cardiovascular response to mental stress, sodium sensitivity, and RBC membrane transport, in particular Na-K cotransport. We will then relate variations in these measures to other correlates of blood pressure already obtained in the population including growth; body composition, Bp tracking, postural change, and endocrine measures. The overall hypothesis is: sodium loading will augment the cardiovascular response to psychogenic stress in blacks at high risk for EH. This response will be linked to changes in Na-K cotransport and the sodium pump.